Electronic musical instrument with plural rc circuits for decay

ABSTRACT

An electronic circuit is disclosed to produce an output voltage which controls the volume of a note produced by a struck key as determined by the velocity with which the key is struck. The electronic circuit includes a changeover switch, changing between two predetermined voltages, coupled to each key of the musical instrument keyboard. The wiper of the switch is connected to ground by a series circuit including a parallel RC network and the cathode-to-anode path of a first diode. A second diode is connected in parallel with the RC network with its cathode being connected to the cathode of the first diode and the output voltage is taken off the cathode of the first diode by the anodeto-cathode path of a third diode. The cathode of this third diode is connected by a second capacitor to ground and is also subjected to an adjustable control voltage.

United States Patent [191 Peltz ELECTRONIC MUSICAL INSTRUMENT WITHPLURAL RC CIRCUITS FOR DECAY [75] Inventor: Gunter Peltz, Wasser,Germany [73] Assignee: ITT Industries, Inc., New York,

[22] Filed: Apr. 5, 1973 [21] Appl. No.: 348,451

[30] Foreign Application Priority Data Apr. 22, 1972 Germany 2219800[52] US. Cl 84/1.l, 84/l.l3, 84/126, 84/ 1.27, 307/262, 307/263, 307/292[51] Int. Cl. Gl0h 1/02 [58] Field of Search 84/1.09, 1.1, 1.13, 1.26,84/ 1.27, DIG. 23; 307/263, 264, 292

[56] References Cited UNITED STATES PATENTS 3,207,952 9/1965 Brahm84/DIG. 23 3,334,249 8/1967 White 307/292 X 3,544,699 12/1970 Harris84/l.26 3,557,296 l/l97l Hirose 84/l.26 3,567,839 3/l97l Dijksterhuis etal 84/l.26 12/1971 Hiyama 84/l.l3

3,651,730 3/1972 Adachi 84/l.26 X

Primary Examiner-Richard B. Wilkinson Assistant Examiner-Stanley J.Witkowski Attorney, Agent, or FirmJohn T. Ol-lalloran; Menotti J.Lombardi, Jr.; Alfred C. Hill [57] ABSTRACT An electronic circuit isdisclosed to produce an output voltage which controls the volume of anote produced by a struck key as determined by the velocity with whichthe key is struck. The electronic circuit includes a changeover switch,changing between two predetermined voltages, coupled to each key of themusical instrument keyboard. The wiper of the switch is connected toground by a series circuit including a parallel RC network and thecathode-to-anode path of a first diode. A second diode is connected inparallel with the RC network with its cathode being connected to thecathode of the first diode and the outputvoltage is taken off thecathode of the first diode by the anode-to-cathode path of a thirddiode. The cathode of this third diode is connected by a secondcapacitor to ground and is also subjected to an adjustable controlvoltage.

9 Claims, 8 Drawing Figures PATENTEUJUN 1 1 191 3816536 SHEET t 0F 4 1ELECTRONIC MUSICAL INSTRUMENT WITH PLURAL RC CIRCUITS FOR DECAYBACKGROUND OF THE INVENTION This invention relates to electronic organsand more particularly to circuit arrangements for influencing the volumeof a struck'tone of an electronic keyboard instrument depending on thekey-striking velocity.

The circuit arrangement shown in FIG. 1 of the accompanying drawing isdisclosed in the GermanPublished Application 2,044,462. Thiscircuitcauses the volume of the struck tone to be dependent on thevelocity at which the key is struck, so that an electronic keyboardinstrument containing this circuit arrangement enables piano-like play.

As shown in FIG. 1 of the drawing, this circuit arrangement includes achangeover switch S, which must be provided for each key of thekeyboard, a parallel- RC (resistor capacitor) network R1 and Cl, and'adiodeDl. The parallel-RC network is connected, at one end, to wiper K ofchangeover switch S and, at the other end, via the cathode-to-anode pathof diode D1 to ground. The break contact of the changeover switch S isconnected to the first d.c. (direct current) voltage potential U whilethe make contact is connected to a second d.c. volate potential U whichin the case of the above cited German Published Application, is ground.The voltage u which determines the volume of the struck tone, is takenoff the cathode of diode D1.

FIG. 2 of the drawing shows the variation of the volume-determiningvoltage a, with respect to time of the arrangement of FIG. 1, it beingassumed that the first d.c. voltage potential U, is negative and thatthe second d.c. voltage potential U is identical to ground potential. Ifthe changeover switch S is operated by depression of a-key, theswitching time t1, which starts when the wiper lifts from the breakcontact and ends when it rests against the make contact, depends as iswell-known on the velocity at which the key is struck. The values of theswitching time t1 of a typical changeover switch were measured to bebetween 2 and ms (milliseconds) were measured.

As long as wiper K contacts the break contact, capacitor Cl is chargedto voltage U through diode D1. If

the changeover switch is operated by depression of the key, capacitor C1will, during the switching time tl, discharge through resistor R1 by avalue depending on the switching time t1. Thus, when contact is madewith the make contact, the a positive pulse is provided at the cathodeof diode D1 whose amplitude A is dependent on the switching time 21 andwhich decays according to an exponential-function.

In FIG. 2, this behavior is illustrated by the triangular curve, withthe leading and trailing edges, corresponding to exponential-functions,drawn as straight lines for simplicity. The slope of the leading edgeduring the rise time t2 depends on the capacitance of capacitor C1 andthe latters loss angle and is therefore practically infinite.

The slope of the trailing edge of the pulse shown in FIG. 2 depends onthe time constant of parallel-RC net work R1 and C1. The trailing edgeof the pulse has a decay time t3.

The just described known circuit arrangement can be used in electronickeyboard instruments only for the register percussion", where, ingeneral, the behavior of a struck or plucked string is imitated. In thiscase the dependence of the volume on the striking speed and the decay ofthe output signal a after the wiper has contacted the make contact areboth governed by the same'time constant, namely, by the time constant ofthe parallel-RC network R1 and Cl. Therefore, if the keystrikingvelocity is to provide a volume variation by the factor 10, aparallel-RC network with a small time constant will be necessary, whilea parallel-RC network with a longer time constant .will be desirable toprovide the tailing edge of the output voltage u,,. It is obvious thatthis cannot be realized with the known circuit.

SUMMARY OF THE INVENTION It is the object of the present invention toeliminate the above-described disadvantage of the known circuitarrangement, so that the time constant determining the volume dependenton the key-striking velocity and the time constant determining thedying-out of the-struck tone are selectable largely independent of oneanother.

Another object of the present invention is to provide a circuitarrangement which not only is suitable for the register percussion whichalso permits during normal organ-playing, i.e. when producing acontinuous tone while the changeover switch is depressed, and duringplay with the register sustain the volume to be determined dependent onthe key-striking velocity. In addition, normal organ-playingis possiblewith a volume independent of the key-striking velocity but having anadjustable onset time and an adjustable dying-out time.

A feature of the present invention is the provision of a circuitarrangement for influencing the volume of a struck tone of an electronickeyboard instrument depending on the key-striking velocity-comprising: adifferent changeover switch associated with each key of the keyboardinstrument, each of the changeover switch having a wiper, a breakcontact connected to a first direct current voltage, and a make contactconnected to a second direct current voltage; a parallelresistor-capacitor network connected to the wiper; ground potential; afirst diode having its cathode-toanode path connected between theparallel network and the ground potential; a second diode connected inparallel to the parallel network having its cathode connected to thecathode of the first diode; a third diode having its anode connected tothe cathodes of the first and second diodes to provide at its cathode avoltage determining the volume of the struck tone; a capacitor connectedbetween the ground potential and the cathode of the third diode; anadjustable control voltage source; and a first resistor connectedbetween the source and the cathode of the third diode.

BRIEF DESCRIPTION OF THE DRAWING Above-mentioned and otherfeatures andobjects of this invention will become more apparent by reference to thefollowing description taken in conjunction with the accompanyingdrawing, in which:

FIG. 1 is a schematic diagram of one known prior art arrangement uponwhich the present invention is based;

FIG. 2 illustrates the waveform of the voltage determining the volume ofthe struck tone;

FIG. 3 illustrates a schematic diagram of one embodiment of theinventive circuit in accordance with the principles of the presentinvention;

FIG. 4 illustrates the waveform of the voltage determining the volume ofthe struck tone employing the embodiment of FIG. 3;

FIG. 5 illustrates a schematic diagram of another embodiment of theinventive circuit in accordance with the principles of the presentinvention;

FIG. 6 illustrates a schematic diagram of still another embodiment ofthe inventive circuit in accordance with the principles of the presentinvention;

FIG. 7 illustrates the waveforms of the circuits of FIGS. 5 and 6, whichdetermines the volume of the struck tone; and

FIG. 8 illustrates a schematic diagram of the inventive circuit inaccordance with the principles of the present invention.

I DESCRIPTION OF THE PREFERRED EMBODIMENTS connected to the cathode ofthe first diode D1. In addi-- tion, the cathode of diode D1 is connectedto the anode-to-cathode path of a third diode D3, from whose cathode istaken the voltage it which determines the volume. The cathode of thethird diode D3 is also connected via a second capacitor C2 to ground,while being subjected to the adjustable control voltage U; via thesecond resistor R2.

In FIG. 3, the adjustability of the control voltage U; is insured by thevoltage U being applied to one end of the potentiometer P1, whose otherend is connected to ground, while its tap is connected to the secondresistor R2. The voltage U;, may bea dc. voltage. Also, a square-wavevoltage adjustable in its mark-to-space ratio may be provided as controlvoltage U3 directly, i.e. without the potentiometer P1, asalreadyproposed in the copending U.S. application of H. Mielke, Ser.

No. 285,683, filed Sept. 1, I972, commonly assigned and now abandoned.In this latter case, a buffer diode must be connected in series withsecond resistor R2 and the input of control voltage U by switches S1 andS2 being placed in the position other than shown. By choosing thecontrol voltage U;, to be a dc. voltage or a square-wave voltageadjustable in its mark-to-space ratio, the decay time 13 of FIG. 2 ismade adjustable, so that the behavior shown as a broken line in FIGS. 2and 4 is obtained during the decay time :3. v

In the circuit arrangement of FIG. 3, part of the charge still stored incapacitor C1 following the changeover of the wiper K is transferred viathe third diode D3 to the second capacitor C2, with the charge splittingup according to the ratio of the capacitance values of these twocapacitors. The discharge of the second capacitor C2 is not, however,determined by resistor R1 of the RC-network because discharge throughthis resistor is prevented by the third diode D3. Instead, the secondcapacitor C2 discharges through the second resistor. R2, which is alsobeing influenced by the applied control voltage U If, for example, thesecond resistor R2 is connected via potentiometer P1 to ground, thedischarge time of the second capacitor C2 is extended and corresponds toan expotential-function, asis indicated by the broken curve in FIGS. 2and 4. If, however, the second resistor R2 is connected via thepotentiometer P1 to a negative control voltage U the discharge curveapproximates a straight line because the discharge of the secondcapacitor C2 takes place toward this negative voltage but is'stoppedabruptly by the diodes D1 and D3 when the discharge curve passes throughzero.

If the circuit of FIG. 3 is operated like the known circuit arrangementwith respect to the two dc. voltage potentials U,.and U i.e. if the dc.voltage potential U is negative and the second d.c. 'voltage potential Uis identical to the ground potential, piano-like playing with theregister percussion is possible in which the volume of the struck toneis dependent on the velocity at which the key is struck, and in whichthe dying-out time of the struck tone, which is identical to the decayt;, or 1 of FIGS. 2 and 4, is adjustable.

If, however, the polarity of the two dc. voltage potentials U and U ischosen conversely, i.e. if the dc. voltage potential U zero, and the dc.voltage potential U zero, organ-playing with the characteristics of theregister sustain is possible whose dying-out time is again adjustablewith the potentiometer P1, but in whichthere is no dependence of thevolume on the velocity at which the keys are struck. FIG. 4 shows thewaveform of the voltage u for this case. It can be seen that, during thekey-depression time T, a continuous tone is produced whose volume fallsoff during the decay time t3 or t3, which is dependent on thepotentiometer. setting. I

The circuit arrangement of FIG. 3, like the circuit arrangements ofFIGS. 5, 6 and 8, to be explained hereinafter, maycontain the resistorR5, which is inserted between the wiper of the changeover switch S andthe anode of the second diode D2 by switches S1 and S2 being placed intheir position opposite to that shown. With this resistor R5, the risetime of the voltage a which time is given by the losses of capacitor C1,can

Y be further influenced. To provide the shortest possible rise time t2,given by the value of resistor R5 for all keys (changeover switches) orfor one or more groups of keys, as is desired e.g. for sacral play(church organ), a square-wave voltage variable in its mark-to-spaceratio may be used instead of the dc. voltage potential U This circuitvariation would be similar to control voltage U as stated hereinaboveand as disclosed in the above-cited co-pending application. As mentionedhereinabove, a buffer diode would also have to be provided in this case,too.

FIG. 5 illustrates a modification of the circuit arrangement of FIG. 3.In this circuit arrangement, one end of the second resistor R2 is nolonger connected directly to the cathode of the third diode D3. Ratherit is connected, on the one hand, via the cathode-toanode path of afourth diode D4 to the cathode of the third diode D3 and, on the otherhand, via the cathodeto-anode path of a fifth diode to the tap of avoltage di-.

vider including the resistors R3 and R4, one of whose terminals isconnected to the wiper K of the changeover switch S, while its otherterminal is connectedto an auxiliary potential U The terminal of thesecond resistor R2 remote from diode D5 is again connected to thecontrol voltage U which may be a dc. voltage adjustable at thepotentiometer P1 and derived from the voltage U or a square-wave voltagevariable in its mark-to-space ratio, in which v case the abovegeous if,as shown in FIG. 6, the tap of the voltage divider including resistor R3and R4 is connected via an impedance-converter stage to the fifth diodeD5. Likewise, the voltage u determining the volume, may be provided viaan impedance converter. In FIG. 6, the two transistors T1 and T2 areprovided for this purpose. Each of transistors T1 and T2 is operated inan emitter-follower configuration and is of the npn-type.

In the arrangement of FIG. 6, the variability of the auxiliary voltageU,, is insured by the fixed auxiliary voltage U, being applied to avoltage divider including resistor R6 and potentiometer P2 connected toground. The variable auxiliary voltage U,, can be taken from the tap ofpotentiometer P2. Thus, the resistor R3 in the embodiment of FIG. 6 isconnected to the tap of potentiometer P2. The fixed auxiliary voltageU,, simultaneously serves as supply voltage for the interconnectedcollectors of transistors T1 and T2.

The emitter of transistor T1 is connected to the anode of the fifthdiode D5, while its base is connected to the tap of the voltage dividerincluding resistors R3 and R4. The base of transistor T2 is connected tothe common junction point of the cathode of the third diode D3, theanode of the fourth diode D4, and capacitor C2, while its emitter, fromwhich the voltage u determining the volume, is taken, is connected viaresistor R7 to ground.

To illustrate the operation of the circuits of FIGS. 5 and 6, it isagain assumed that the d.c. voltage potential U, is negative, while thed.c. voltage potential U is identicalto the ground potential. When thechangeover switch S is operated, the voltage across the second capacitorC2 first jumps to the amplitude A of FIG. 7 and then, during the timeat3, drops to the value A, which is determined by the value of thevariable auxiliary voltage U, in such a manner that the discharge ofcapacitor C2 through resistor R2 toward the control voltage U,, is overwhen the fourth diode D4 is cut off. Thus the level A is adjustable atwill by means of the variable auxiliary voltage U,. When the changeoverswitch S is released, i.e., when its wiper rests against the breakcontact again, capacitor C2 again discharges, as in the case of FIG. 3,during the time (l-a)l3. The discharge interrupted by diode D4 is thuscontinued after the changeover switch S has returned to its initialposition.

. The slope of the falling portion of the curve is again selectable bymeans of the control voltage U,, as is indicated in FIG. 7 by the brokenlines and by the associated times at3 and (l-a)t3'.

With the circuit arrangements of FIGS. 5 and 6, the following four modesof operation are possible:

I. U, 0, U 0, U, or U, and variable:

In this case, normal organ-playing with a volume depending on thekey-striking velocity is possible, the dying-out time being selectablevia the potentiometer P1.

In this case, play as stated hereinabove in connection with FIG. 3 forU, 0 and U 0 is possible, i.e. pianolike playing or organ playing withthe register percussion, with the volume depending on the key-strikingvelocity and with the dying-out time controlled by the potentiometer P1.

This case corresponds to the case described hereinbefore with referenceto FIG. 3 for U, 0 and U, 0, i.e. organ register sustain with dying-outtime controlled by the potentiometer P! but without dependence of thevolume on the key-striking velocity.

4. U, slightly negative, U slightly positive, U,, or U,

O and variable:

This case corresponds to the curve shown in FIG. 7 and permitsguitar-like play, with the volume of the value A depending on thekey-striking velocity.

Regarding the effect to be achieved, the circuit arrangements accordingto this invention are thus usable in a multiple manner, which can beachieved by simply reversing the polarity of the two d.c. voltagepotentials U,, U and of the auxiliary potential U, or U.,'. Hence, thesame components can be used for the registers percussion and sustain, sothat considerable component savings can be achieved.

FIG. 8 shows a preferred modification of the circuit arrangement of FIG.3. Connected in parallel to the anode-to-cathode path of the third diodeD3 is the emitter-to-collector path of the npn transistor T3. The baseof the npn transistor T3 is either open-circuited or connected toground. In the former case, the anode of the first diode D1 issimultaneously connected to ground, while in the latter case the anodeof the first diode D1 is simultaneously open-circuited. This isillustrated in FIG. 8 by the changeover switch S, whose wiper K isconnected to ground and contacts either the anode of diode D1 or thebase of the npn transistor T3. If necessary, a collector resistor R8 maybe inserted between transistor T3 and the second capacitor C2 byswitches S3 and S4 being moved to their position other than that shown.Regarding the choice and application of the control voltage U,,, theremarks made in connection with FIG. 3 apply analogously.

With the circuit arrangement of FIG. 8, the following modes of operationare possible:

I. U, 0, U 0, U,, s 0 or square-wave voltage, the base of transistor T3open-circuited; and the anode of diode D3 connected to ground:

The amplitude response corresponds to that of FIG. 4, i.e. normalorgan-playing is possible whose volume is not dependent on thekey-striking velocity. The amplitude A is determined by the value of thed.c. voltage potential U while the rise time t2 is determined by thevalue of resistor R5, which may be provided, or by the loss resistanceof the capacitor C2 and by the latters value, while the decay time t3depends on the values of the capacitor C2 and of resistor R2.

If the control voltage U,, is made negative, the decay time isshortened. By the use of the square-wave voltage variable in itsmark-to-space ratio, the decay time can be extended with the exponentialdecay characteristic being maintained, so that play with the register ispossible sustain.

If the d.c. voltage potential U,, is replaced by such a square-wavesignal, the rise time can be extended (sacral play", see above).

2. U 0, U 0, U, s or square-wave voltage; base of transistor T3open-circuited; and the anode of diode D1 connected to ground:

In this case, piano-like play with operated pedal or organ-playing withthe register percussion is possible, with the volume depending on thekey-striking velocity. The amplitude response corresponds to that ofFIG. 2. The decay time 13 behaves as described in l. above. The decayprocess is not influenced by the release of the key S, so that the tonefades away slowly even if the strike is very short.

3. U, 0, U 0, U 0 or square-wave voltage base of transistor T3 connectedto ground; and the anode of diode D1 open-circuited:

In this case, piano-like playing without operation of the pedal ispossible, with the volume depending on the key-striking velocity, asshown by the curve of FIG. 2, but with an abrupt break-off of thedecaying portion of the curve. The reason for this abrupt break off isthat the transistor T3 is rendered conductive as soon as the wiper Kcomes into contact with the dc. voltage potential U after the release ofthe changeover switch (key) S, so that capacitor C2 discharges rapidly.The duration of this rapid discharge is determined to a first degree ofapproximation by resistors R5 and R8 and capacitor C2. If the resistorsR5 and R8 are not provided, i.e. if R5 R8 0, it is possible that thecollector-to-emitter saturation resistance of transistor T3 must betaken into account, too.

4. U 0, U 0, U 0 buffer diode the base of transistor T3 connected toground; and the anode of diode D1 open-circuited:

In this case, organ-playing with the volume depending on thekey-striking velocity is possible. This corresponds to case no. 3 with avery long dying-out time (percussion"). After the operation of thechangeover switch (key) S, the output voltage u jumps to the valuedetermined by the key-striking velocity and decreases slowly becausecapacitor C2 can discharge only through its leakage current and throughthe base current of transistor T2, so that virtually no decrease involume can be noticed for several seconds. When the key is released,capacitor C2 discharges very rapidly as stated in 3 above;

5. U slightly negative, U slightly positive, U s O or square-wavevoltage the base of transistor T3 open-circuited; and the anode of diodeD2 connected to ground:

This permits a combination of the registers percussion and sustain to berealized, with the duration of the dying-out (sustain) determined by thevalue of U The amplitude response thus corresponds to that of FIG. 7,with the value A determined by U,, the 'value A by U and the value of t3or t3 by U However, if the base of transistor T3 is connected to groundand the anode of diode D1 is open-circuited the output voltage u,,becomes zero as soon as the key S is released.

The circuit arrangements of FIGS. 5 and 8 are thus adjustable to therespective manner of play simply by switching, or reversing the polarityof, potentials, i.e. this switching of the potentials is effected onlyonce for the entire electronic musical instrument, so that the number ofcomponents necessary for switching is small.

If the control voltage U is replaced by the above- 6 mentionedsquare-wave voltage of variable mark-tospace ratio or becomes positiveas stated in 4., a buffer diode must be connected in series withresistor R2 by switches S1 and S2, as mentioned hereinbefore withreference to FIG. 3.

The given polarities of the'd.c. voltage potentials U U of the controlvoltage U;,, and of the auxiliary potential U, or U, as well as thedirection of the diodes D1 to D5 as shown in the figures and defined inthe claims and the conducitvity type of the transistors TI and T2 npntype (in FIGS. 6 and 8) may, of course, be replaced by the oppositepolarities by the other direction and the opposite conductivity typewithout departing from the scope of the present invention.

In the literature, the curves shown in FIGS. 2, 4, and 7 are referred toas envelopes" because this shape corresponds to the amplitude responseof the struck tone. As was shown, the envelope of FIG. 7 represents theaddition of the envelopes of FIGS. 2 and 4, the position of the value Abeing determined by the auxiliary potential U, or U, (FIGS. 5 and 6) orby the dc. voltage potential U (FIG. 8). If, in FIGS. 5 and 6, thispotential is equal to the potential U the value A is zero (percussion).

While I have described above the principles of my invention inconnection with specific apparatus it is to be clearly understood thatthis description is made only by way of example and not as a limitationto the scope of my invention as set forth in the objects thereof and inthe accompanying claims.

I claim:

1. A circuit arrangement for influencing the volume of a struck tone ofan electronic keyboard instrument depending on the key-striking velocitycomprising:

a changeover switch for each key of said keyboard instrument, each ofsaid changeover switches being directly connected to its associated oneof said keys and each of said changeover switches having a wiper,

a break contact connected to a first direct current voltage, and

a make contactconnected to a second direct current voltage;

a parallel resistor-capacitor network connected to said wiper; groundpotential;

a first diode having its cathode-to-anode path connected between saidparallel network and said ground potential;

a second diode connected in parallel to said parallel network having itscathode connected to the cathode of said first diode;

a third diode having its anode connected to the cathode of said firstand second diodes, said third diode providing at its cathode a voltagedetermining the volume of the struck tone;

a capacitor connected between said ground potential and the cathode ofsaid third diode;

an adjustable control voltage source; and

a first resistor connected between said source and the cathode of saidthird diode.

2. A circuit arrangement according to claim 1, further including afourth diode having its anode-to-cathode path connected between thecathode of said third diode and said first resistor;

an auxiliary potential;

a voltage divider connected between said auxiliary potential and saidwiper; and

9 10 a fifth diode having its cathodeto-anode path confirst diode.

nected between the cathode of said fourth diode 6. A circuit arrangementaccording to claim 5, furand a tap of said voltage divider. therincluding 3. A circuit arrangement according to claim 2, fura collectorresistor connected between the collector ther including of said npntransistor and the cathode of said third an impedance converterconnected between the diode.

anode of said fifth diode and said tap of said volt- 7. A circuitarrangement according to claim 1, furage divider. ther including 4. Acircuit arrangement according to claim 3, a series resistor connectedbetween said wiper and wherein said parallel network.

said impedance converter is an emitter follower tran- 8. A circuitarrangement according to claim 1,

sistor. wherein 5. A circuit arrangement according to claim 1, fursaidadjustable voltage source is an adjustable direct ther including currentvoltage source, said first resistor being di an npn transistor havingits emitter-to-collector path 5 rectly connected to said adjustabledirect current connected in parallel with the anodeto-cathode voltagesource. path of said third diode; and 9. A circuit arrangement accordingto claim 1, a switch having a first position to open-circuit the whereinbase of said npn transistor and to simultaneously said adjustablevoltage source is a source of square connect the anode of said firstdiode to said ground wave voltage having an adjustable mark-to-spacepotential and a second position to connect the base ratio, said firstresistor being connected to said of said npn transistor to said groundpotential and source of square wave voltage by a buffer diode. tosimultaneously open circuit the anode of said

1. A circuit arrangement for influencing the volume of a struck tone ofan electronic keyboard instrument depending on the keystriking velocitycomprising: a changeover switch for each key of said keyboardinstrument, each of said changeover switches being directly connected toits associated one of said keys and each of said changeover switcheshaving a wiper, a break contact connected to a first direct currentvoltage, and a make contact connected to a second direct currentvoltage; a parallel resistor-capacitor network connected to said wiper;ground potential; a first diode having its cathode-to-anode pathconnected between said parallel network and said ground potential; asecond diode connected in parallel to said parallel network having itscathode connected to the cathode of said first diode; a third diodehaving its anode connected to the cathode of said first and seconddiodes, said third diode providing at its cathode a voltage determiningthe volume of the struck tone; a capacitor connected between said groundpotential and the cathode of said third diode; an adjustable controlvoltage source; and a first resistor connected between said source andthe cathode of said third diode.
 2. A circuit arrangement according toclaim 1, further including a fourth diode having its anode-to-cathodepath connected between the cathode of said third diode and said firstresistor; an auxiliary potential; a voltage divider connected betweensaid auxiliary potential and said wiper; and a fifth diode having itscathode-to-anode path connected between the cathode of said fourth diodeand a tap of said voltage divider.
 3. A circuit arrangement according toclaim 2, further including an impedance converter connected between theanode of said fifth diode and said tap of said voltage divider.
 4. Acircuit arrangement according to claim 3, wherein said impedanceconverter is an emitter follower transistor.
 5. A circuit arrangementaccording to claim 1, further including an npn transistor having itsemitter-to-collector path connected in parallel with theanode-to-cathode path of said third diode; and a switch having a firstposition to open-circuit the base of said npn transistor and tosimultaneously connect the anode of said first diode to said groundpotential and a second position to connect the base of said npntransistor to said ground potential and to simultaneously open circuitthe anode of said first diode.
 6. A circuit arrangement according toclaim 5, further including a collector resistor connected between thecollector of said npn transistor and the cathode of said third diode. 7.A circuit arrangement according to claim 1, further including a seriesresistor connected between said wiper and said parallel network.
 8. Acircuit arrangement according to claim 1, wherein said adjustablevoltage source is an adjustable direct current voltage source, saidfirst resistor being directly connected to said adjustable directcurrent voltage source.
 9. A circuit arrangement according to claim 1,wherein said adjustable voltage source is a source of square wavevoltage having an adjustable mark-to-space ratio, said first resistorbeing connected to said source of square wave voltage by a buffer diode.